A stereoscopic 3D display usually presents an observer with images with parallax from individual right and left eye viewpoints. There are two methods of providing the two eyes of the observer with the parallax images in a time sequential manner. In one method, the observer utilizes a pair of shutter or 3D glasses which transmit or block light from the viewer's eyes in synchronization with alternating the left/right image display. Similarly, in another method, right eye and left eye viewpoints are alternatively displayed and presented to the respective eyes of the observer but without the use of 3D glasses. This second method is referred to as autostereoscopic and is sometimes desirable for stereo 3D viewing because separate glasses are not needed though there is limited permissible head motion.
A liquid crystal display (LCD) is a sample and hold display device such that the image at any point or pixel of the display is stable until that pixel is updated at the next image refresh time, typically 1/60 of a second or faster. In such a sample and hold system, displaying different images, specifically displaying alternating left and right images for an autostereoscopic display, requires careful timing sequencing of the light sources so that, for example, the left eye image light source is not on during the display of data for the right eye and vice versa.
Turning on the light source to light the first or right image at time t=0 provides light to the right image. At time t=16.67 ms (typical 60 Hz refresh rate) the second or left image starts to be put in place. The second image replaces the first image and can take 16.67 ms to complete the transformation. Current systems turn off all the light sources that illuminate the first or right image and then turn on all the light sources that illuminate the second or left image at sometime during the second image transformation. This can lead to “cross-talk” or “ghosting” of the first or right image in the second or left image, degrading the stereoscopic 3D effect. An additional source of crosstalk in current systems is light reflection from a left or right source off of the opposite source window backwards toward the original source.